i BYZANTINE ARCHITECTURE 3 the dome rests upon the outer walls of the buildings. Both are foundations of Justinian the Great. Of the Cross church plan showing the cross externally at the ground level no example survives in the city. But at least one church of that form was seen at Constantinople in the case of the church of the Holy Apostles. This was essentially a mausoleum^ built originally by Constantine the Great and reconstructed by Justinian to contain the sarcophagi of the sovereigns and the patriarchs of New Rome.1 The church of S. Mark at Venice was built on the plan of the Holy Apostles. It is a cruciform church with aisles^ but the galleries which might have been expected above them are omitted. The central dome rests on four pierss and four smaller domes cover the arms. Professor Strzygowski gives examples of cross-planned cells in the catacombs of Palmyra,2 and in many Eastern rock tombs.3 Such cross plans are found also in the Roman catacombs. These subterranean chapels^ of course3 do not show the external treatment, yet there can be little doubt that the external cross plan was originally sepulchral, and owes its peculiar system of planning to that fact. On the other hand, it was adopted in such churches as S. Mark's at Venice and in the French examples of P£rigord for aesthetic or traditional reasons. In passing now to a consideration of the distinct forms developed from these pre-Byzantine types of church build-ing3 the classification adopted by Professor Strzygowski may be followed. In his Kleinasien he has brought forward a series of buildings which show the manner in which a dome was fitted to the oblong basilica^ producing the domed basilica (Kftppelba$ilica\ an evolution which he regards as Hellenistic and Eastern. In contrast to this, Strzygowski distinguishes the domed cross church (Kreutzkiipfelkirche\ of which S. Theodosia in Constantinople (p. 170) is the typical example and which is a Western development. A 1 Dtlrm, Handbuch, Part II. vol. iii. pp. 115, 14.9. A "restored plan Is given in Lethaby's Mediaeval Art, p, 47. 2 Orient oder Rotn, p. 19. 3 Kleinasien, p. i$z.